1. Field of the Invention
The present invention relates to a method of making an optical fiber ribbon in which a plurality of coated optical fibers are arranged in a plane and bundled together into a tape form.
2. Related Background Art
In an optical fiber ribbon, a plurality of coated optical fibers arranged in parallel are bundled together as being coated with a collective coating material made of an ultraviolet curable resin. In the conventional method of making an optical fiber ribbon, after a plurality of coated optical fibers are collectively coated with an ultraviolet curable resin, thus coated ultraviolet curable resin is irradiated with an ultraviolet ray in an ultraviolet irradiation apparatus so as to be cured. Here, as an ultraviolet lamp for generating the ultraviolet ray emits light, a considerable amount of heat is generated. Due to this heat, the collective coating material is softened and, in this state, comes into contact with other hard materials, whereby the surface of the optical fiber ribbon may be damaged, or the coated optical fibers may be negatively effected by micro-bendings.
In order to overcome such a problem, for example, in Japanese Patent Application Laid-Open No. 1-191110, an optical fiber ribbon is produced while a cooling gas is caused to flow into an ultraviolet irradiation (curing) apparatus so as to make the surface temperature of the optical fiber ribbon lower than the glass transition temperature of the ultraviolet curable resin. Also, in this publication, a plurality of stages of ultraviolet irradiation apparatus each having an output not greater than a predetermined level are provided, and an optical fiber ribbon is produced while the surface temperature of the optical fiber ribbon in the ultraviolet-curing process is made lower than the glass transition temperature of the ultraviolet curable resin.
In Japanese Utility Model Application Laid-Open No. 2-149904, on the other hand, cooling water is caused to flow through a hollow portion in the vicinity of the outer periphery of a capstan for pulling an optical fiber ribbon coated with an ultraviolet curable resin, thereby cooling the cured optical fiber ribbon.